The production of an active, stereoregular catalyst for the polymerization of alpha-olefins (particularly polypropylene) is frequently a complicated process with much of the complexity being encountered during the production of the olefin polymerization procatalyst. This procatalyst is frequently a titanium-containing solid and often contains moieties of magnesium and halide, particularly chloride. One class of procatalyst (as described in U.S. Pat. No. 4,728,705 to Nestlerode et al which is incorporated herein by reference) results from the reaction of a magnesium compound, often a magnesium alkoxide compound, with a tetravalent titanium halide in the presence of a reaction diluent and an electron donor which is often an alkyl ester of an aromatic monocarboxylic or dicarboxylic acid. The procatalyst is generally a solid material and is easily separated from the media of its production. The remaining waste product is a liquid material which contains at least some of unreacted titanium tetrahalide, reaction diluent, unreacted electron donor, and a wide array of titanium haloalkoxide compounds or complexes thereof with other titanium haloalkoxide compounds or aromatic esters.
This waste product presents a substantial disposal problem which adversely affects the economy of the polymerization process. It would be of advantage to be able to separate the components of such a waste stream and to recover for reuse the more valuable components of the product, such as titanium tetrahalide and the reaction diluent.
One such method of component separation is described in U.S. Pat. No. 5,242,549 to Potter et al. which provides for the separation of waste product components by a method wherein a separation solvent is added to the waste product, and the liquid components are separated by distillation. However, this process, disadvantageously, requires the use of two distinct solvents, a reaction diluent and a separation solvent.